The Local structure is 2104 bytes long and jemalloc rounds this to 4096 bytes.

[PaulBone]

The Local structure here https://searchfox.org/mozilla-central/source/third_party/rust/crossbeam-epoch/src/internal.rs#287 is 2104 bytes long. When compiled into Firefox and using the jamalloc memory allocator this is rounded up to 4096 bytes (a very common practice). This wastes just under 12KB for a Firefox process that loads a simple website. It'd be nice if it could allocate 2048 bytes or less saving this memory.

Thanks.

[taiki-e]

Local::bag field is 2056 bytes and already exceeds 2048 bytes, so there seems to be no other way to do this than reduce the size of Bag.

crossbeam/crossbeam-epoch/src/internal.rs

Lines 362 to 363 in bfb7705

	/// The local bag of deferred functions.
	pub(crate) bag: UnsafeCell<Bag>,

And to reduce the size of the Bag, it needs to reduce MAX_OBJECTS.

crossbeam/crossbeam-epoch/src/internal.rs

Lines 56 to 67 in bfb7705

	/// Maximum number of objects a bag can contain.
	#[cfg(not(feature = "sanitize"))]
	const MAX_OBJECTS: usize = 64;
	#[cfg(feature = "sanitize")]
	const MAX_OBJECTS: usize = 4;
	/// A bag of deferred functions.
	pub struct Bag {
	/// Stashed objects.
	deferreds: [Deferred; MAX_OBJECTS],
	len: usize,
	}

@stjepang: Is it okay to reduce MAX_OBJECTS? Or do you think we need to think of another way?

[ghost]

It should be totally fine to reduce it to 31 (if my calculation is right).

[PaulBone]

Awesome thanks.

[taiki-e]

Reopening -- #552 has been reverted in #879. (See #869 for the context.)